Unlike Bike Week or Bike to Work Day, Bicycle Day has less to do with a means of transport than it does with the trip itself. In particular, it denotes the day in 1943 when Dr. Albert Hofmann first dropped Lysergic acid diethylamide (LSD). Hofmann accidentally discovered the compound a few days before and became curious about what would happen if he ingested what he calculated to be a suitably tiny amount. 250 micrograms and a bike ride home brought the Swiss scientist an answer to that question. The scientist was plagued with feelings of intense anxiety, paranoia, and a fear of impending insanity. After Hofmann determined that he was not in danger, he began to enjoy the trip—complete with its fascinating patterns, images, and colors.

Bicycle Day has been informally celebrated since 1985, when the commemoration was first suggested by a professor at Northern Illinois University. It’s a fine date for a pleasant bike ride and an opportunity to learn about the history of psychedelics. You could even host a painting party to capture the vivid, fantastical imaginings of the human mind on canvas.